This invention relates to a semiconductor device and, more particularly, to a method for fabricating a semiconductor device in the form of a multi-layered interconnection structure.
Fabrication of a multi-layered interconnection structure of semiconductor devices has been known, for example, in Japanese Non-examined Patent Publication No. Hei 2-209753. According to this known method, an Al lower wiring layer 502 is formed on an Si substrate 501 as is shown in Fig. 1(a), on which a 0.2-0.3 .mu.m thick plasma-deposited SiO.sub.2 film 503 is formed as shown in FIG. 1(b).
Subsequently, an about 2 .mu.m thick TEOS-SiO.sub.2 film 404 is formed, as shown in FIG. 1(c), at a temperature of 350.degree. C. according to a atmospheric atmospheric vapor phase deposition using tetraethyl orthosilicate (TEOS) and ozone as source gases. As shown in FIG. 1(d), a plasma-deposited SiO.sub.2 film 505 is formed on the film 504. Thereafter, a photoresist film 506 for forming through-holes in position is formed according to a known photolithographic technique (Fig. 1(e)). A through-hole is formed by etching of the film 506. As shown in FIG. 1(f), an Al upper wiring layer 507 is formed. Finally, in order to ensure good electric connection between the Al lower wiring layer and the Al upper wiring layer, the multi-layered structure is wholly heated to a temperature of about 380.degree. C.
However, the above prior art has the following disadvantages. The silicon oxide film which has been formed by the atmospheric pressure chemical vapor deposition using ozone and tetraethyl orthosilicate as the source gases has a high tensile stress. When the film is formed in a thickness of not lower than 1.5 .mu.m under which it is etched back, irregularities will be left with the possibility that tile electrode layer formed on the film will suffer disconnection thereof. Since the film-forming temperature is so high as 350.degree. C., great thermal stress is produced in the inside of the film, with voids being apt to be produced in the Al wirings, thereby causing disconnection of the Al wirings. In addition, the thus formed silicon oxide film has moisture left in large amounts and has a high moisture absorption, resulting in the problem that the film is poor in moisture proofing.